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Photochemically-Driven CO2 Release Using a Metastable-State Photoacid for Energy Efficient Direct Air Capture


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Direct air capture (DAC) technologies that extract carbon dioxide directly from the atmosphere are critical for mitigating effects of climate change. Sorbent regeneration and release of captured CO2 require an enormous amount of energy, making large-scale deployment economically prohibitive. State-of-the-art technologies use heating systems to provide very high temperature and energy to overcome the inherent stability of the CO2-bound complexes formed in liquid solvents. This new technology uses light instead of heat to achieve release of CO2 captured using an aqueous solution of amino acids (AAs). Photoacids offer an attractive means to photochemically drive efficient release of the CO2 through a deliberate proton transfer reaction using light from the sun. 


This technology for direct air capture is a photochemically-driven approach for CO2 release by exploiting the unique properties of photosensitive compounds. Amino acid-based DAC systems show the potential of the photosensitive compounds such as photoacids to be used for CO2 release cycles by regulating pH changes and associated isomers driven by light. Photoacids are known to dramatically lower the solution pH – upon optical excitation with either UV or visible light. This offers an attractive means to photochemically drive efficient release of the CO2 through a deliberate proton transfer reaction using light from the sun. This technology is based on an AA sorbent and a metastable state photoacid driven photochemical release of CO2. Upon irradiating with moderate intensity light, conversion of total inorganic carbon (bicarbonates/carbonates and carbamates) to CO2 was found for the simulated and amino acid-based DAC systems. This confirms the feasibility of on-demand CO2 release under ambient conditions using light instead of heat, thereby providing an energy efficient pathway for the regeneration of DAC sorbents. For commonly used thermal-swing approaches, the high temperatures needed for the CO2 release and sorbent regeneration, which can be as high as 900 C in the aqueous solvents case, can cause significant oxidation and thermal degradation of the capture agent over time. Furthermore, extensive heating and boiling of aqueous solvents wastes a lot of energy. This technology using light to regenerate DAC solvents at ambient conditions avoids these problems altogether. 

Applications and Industries

  • Energy 
  • Carbon capture 
  • On-demand CO2 release   
  • CO2 conversion into value-added products 


  • Aids in achieving clean energy goals 
  • Heating and associated energy costs not required 
  • Light irradiation can be adjusted for various needs 
  • Uses sunlight, which is free


To learn more about this technology, email or call 865-574-1051.